Anti-fogging and anti-plumming disulfide compound for use in silver halide photographs



United States Patent US. Cl. 9666.5 14 Claims ABSTRACT OF THE DISCLOSURE A light-sensitive photographic element, a silver halide emulsion therefor and an aqueous developer solution which contain as an anti-fogging and anti-plumming material a compound of the general formula:

COOR COOR HO OH where R can be hydrogen, sodium, potassium, ammonium, NR R R R where R R R and R, can be hydrogen, alkyl of 1 to 4 carbon atoms and hydroxy alkyl and X can be hydrogen, alkyl of 1 to 4 carbon atoms, chlorine, bromine, alkoxy and hydroxy alkyl where the alkyl group in the last two substituents contains from 1 to 4 carbon atoms.

This invention relates in general to photography and in particular to the provision of novel stabilizing compounds for use in connection with the preparation and/ or processing of photographic silver halide emulsions.

It is well known that light-sensitive materials such as gelatin-silver halide emulsions exhibit a marked tendency to fog. The term fog as used in the photographic art connotes that portion of the density obtained upon development which arises by virtue of factors other than the photographic exposure. The fog may be attributable to a number of influences including for example, excessive ripening of the emulsion, prolonged storage of the film and especially under conditions of elevated temperature and/or humidity, as well as by prolonged development of the exposed emulsion and the like. In general, the fog may be of two types, namely, yellow fog and chemical gray) fog. The yellow fog, sometimes referred to as colored or dichroic fog, is essentially a colloidal deposit of silver, the color intensity and general appearance of which are determined by the minute particle size and degree of subdivision. The fog is chiefly yellow in color and is most apparent in the lighter portions of the negative. The color may vary, however, and the colloidal silver particles may, for example, appear green by reflected light and yellow or red by transmitted light.

On the other hand, the so-called chemical fog, or gray fog, is the more common and is formed in a number of ways. As mentioned hereinbefore, such fog may be caused by the nucleation of silver halide grains due to inadvertent exposure, excessive ripening of the emulsion, storage of the film under severe conditions of temperature and/or humidity, etc. Fog may also be caused by exposure to chemicals, for example, hydrogen sulfide and other reactive sulphur compounds, hydrogen peroxide vapors and strongly reducing materials such as those present in the developer solution. In any event, and irrespective of the cause, the fog will usually manifest itself as a spurious density extant over the entire area of the sensitive coating and typically, is substantially non-uniform.

To overcome or otherwise alleviate the aforedescribed disadvantages it has become a recognized practice in the photographic art to add certain chemical stabilizer compounds to the light sensitive emulsion at some stage of its preparation which purportedly function to enhance their photographic stability to an appreciable extent. However, in the vast majority of instances, the stabilizing and anti-fogging compounds heretofore employed for such purposes have provided only marginal improvement since they are often characterized by the disadvantage that upon addition to the emulsion they cause a loss of speed and/ or contrast of the emulsion or otherwise deleteriously affect its sensitometric characteristics. The loss in speed is particularly pronounced in those regions of the spectrum to which the emulsions are optically or dye sensitized.

A further problem frequently encountered with photographic silver halide emulsions currently available commercially relates to the difiiculties associated with attempts to achieve as well as maintain maximum image density. Silver halide emulsions after exposure invariably exhibit a tendency towards image decolorization during processing, i.e., during development, fixing, washing, toning, etc. Such a tendency becomes particularly pronounced when such emulsions encounter the moist heat to which they are exposed on drying as is the case when prints are subjected to ferrotyping or hot glazing. The tendency to decolorize will be manifested by a shift as Well as loss of intensity in the image obtained upon development with the result that the developed silver image displays an undesired color commonly referred to in the photographic art as plumming or bronzing. Remedial techniques heretofore promulgated for purposes of mitigating the aforedescribed problems such as those based on the use of chemical additives have likewise been accompanied by manifold drawbacks including for example the decided tendency of such compounds to reduce the sensitivity of the silver halide emulsion.

In accordance with the discovery forming the basis of the present invention, it has been found that both the antifogging and anti-plumming characteristics of light-sensitive silver halide emulsions can be synergistically modified to advantage by the utilization of a particular class of chemical compounds in connection with the preparation and/or processing of such emulsions.

Thus, a primary object of the present invention resides in the provision of improved anti-fogging and anti-plum ming compounds in which the foregoing and related disadvantages are eliminated or at least mitigated to a substantial degree.

Another object of the present invention resides in the provision of light-sensitive emulsions containing a compound which stabilizes the emulsion against fogging and plumming while exhibiting little, if any, tendency to reduce the speed and/ or contrast of the emulsion.

A further object of the present invention resides in the provision of light-sensitive emulsions and photographic elements prepared therewith containing an anti-fogging compound which is substantially devoid of any tendency to reduce the sensitivity of the emulsion to light of longer wave length due to the presence of one or more sensitizing dyes.

A still further object of the present invention resides in the provision of a process for the treatment of an exposed photographic silver halide emulsion wherein at least one of the steps of developing, fixing, washing, drying, etc., said emulsion is effected in the presence of a novel stabilizing compound to be more fully described hereinafter.

The attainment of the foregoing and related objects is made possible in accordance with the broader aspects of the present invention by the incorporation in a lightsensitive photographic element, e.g., silver halide emul- 3 sion, developing solution and/or other processing solution associated therewith, of a material comprising a compound of the following general formula:

I ROOC COOR HO OH wherein R represents hydrogen or a water-solubilizing cation such as alkali metal, e.g., sodium, potassium, etc.; ammonium; substituted ammonium in which one or more of the hydrogens is replaced by lower alkyl preferably containing from 1 to 4 carbon atoms, e.g., methyl, ethyl, etc; hydroxy lower alkyl, e.g., hydroxy ethyl and wherein such substituents may be the same or different.

The improvements provided by the present invention are particularly manifest with the use of compounds wherein the COOR and -OH groups are substituted upon adjacent carbon atoms in each of the phenyl moieties. Such compounds can be represented by the following structural formula:

II B000 (7003.

HO OH wherein R has the meanings given above.

It will further be understood that each of the phenyl rings in the above depicted formulae may contain further inert, innocuous substituents including, for example, alkyl and preferably lower alkyl of 1 to 4 carbon atoms, e.g., methyl, ethyl, propyl, isobutyl, etc.; halogen, e.g., chloro, bromo, etc.; lower alkoxy, e.g., methoxy, ethoxy, etc.; hydroxy lower alkyl, e.g., hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, etc.

Compounds encompassed by the foregoing formulae may be readily prepared by reacting the corresponding hydroxy benzoic acid with chlorosulfonic acid to form the sulfonyl chloride derivative and thereafter treating the later compound with a mixture of glacial acetic acid and hydrogen iodide to form the corresponding disulfide derivative.

The disulfide compounds thus produced may be readily converted to its salt by treating same with a compound containing the desired cation such as sodium carbonate, potassium carbonate, silver nitrate, ammonium carbonate and the like.

Improved fog reduction, anti-plumming and other beneficial efiects are obtained when the aforementioned compounds are incorporated into the silver halide emulsion as ripening finals or as coating finals. As is well known, ripening finals are added during the ripening or sensitivity increasing stage of the emulsion making process. Such additions may be effected before, during or after the decomposition of the soluble silver salt such as silver nitrate by means of a soluble halide such as potassium bromide, sodium chloride or the like in the presence of a suitable colloid carrier such as gelatin, polyvinyl alcohol, solubilized casein, albumen or the like.

Coating finals are added to the emulsion just prior to coating on a suitable support such as glass, paper or afilm at a time when the emulsion has nearly attained its maximum sensitivity.

It will also be understood that the novel stabilizers of the present invention may be incorporated in a layer adjacent to the sensitized layer such as an anti-abrasion layer. The stabilizing compound may be utilized in concentrations varying over a relatively wide range; for example, when added to the light sensitive silver halide emulsion layer as a ripening final, it is found that optimum realization of results provided herein are assured with stabilizer concentrations ranging from as low as .02 milligram up to about 500 milligrams per 0.6 mole of silver halide. The concentration selected within the aforestated range will depend to a large extent on the type of emulsion employed and thus it is advisable to determine the optimum concentration from case to case. If added during the emulsion preparation stage, stabilizer concentrations on the order of approximately one-tenth of those employed when adding the stabilizer as a coating final are found to be quite suitable.

The improved anti-plumming effects made possible by the present invention are particularly pronounced with the use of the above described compounds in the higher concentration ranges. For example, particularly beneficial results obtain with the use of the disulfide stabilizers in concentrations ranging from about 10 to 500 milligrams per 0.6 mole of silver halide.

Novel sensitizer compounds included within the ambit of the above depicted structural formula can be applied in a variety of ways to impart stability to photographic elements. As previously mentioned, they may be included as a constituent of the emulsion layer, of a surface layer over the emulsion or alternatively, over the base or support.

Further embodiments of the present invention contemplate the addition of such compounds to at least one of the developing, fixing, washing, drying, etc. solutions utilized in the processing of the exposed emulsion. For example, when utilized in the washing step the stabilizer can be applied to the otherwise finished photographic element by immersing same in an alcohol, e.g., methanol or alcohol-water solution in the case of the free acid derivatives while the salt derivatives may be employed effectively as simple water solutions.

In general, it is found that the improvements provided by the present invention are particularly manifest according to procedures whereby development is effected in the presence of said stabilizer compounds. This, of course, would be the case should the stabilizer be included in the light sensitive photographic element, the developing solution and/or a suitable prebath. In any event, when incorporated into the photographic developer or other processing bath, the stabilizers of the present invention are preferably employed in concentrations ranging from about 1 to about 50 milligrams per liters of solution, with a range of about 5 milligrams to about 20 milligrams per liter being particularly preferred.

In addition to being useful in orthochromatic and panchromatic emulsions, the stabilizers may also be used in non-sensitized emulsions, X-ray emulsions, paper emulsions, color emulsions and the like. If used with sensitizing dyes, they may be added to the emulsion before or after dye addition. Moreover, the present stabilizers may also be employed in conjunction with other known antifoggants and stabilizers, reduction stabilizers, metal and noble metal sensitizers or in combination with other additive agents and the like.

The stabilizer may also be employed in gelatin or other water-permeable colloids including polyamides or a mixture of gelatin with a polyamide as described in US. Patent 2,289,775; polyvinyl alcohol and jelling compound as described in US. Patent 2,249,537; polyvinyl acetaldehyde acetal resins and partially hydrolyzed acetate resins described in US Patents 1,939,422 and 2,036,092; cellulose derivatives, e.g., cellulose nitrate, cellulose acetate, and the lower fatty acid esters of cellulose including simple and mixed esters and ethers of cellulose and the like.

When preparing the photographic emulsion in accordance with the present invention, a solution of the stabilizer in a suitable solvent, such as water, alcohol, dimethyl formamide or alcohol-water mixture adjusted to a neutral or slightly alkaline pH, i.e., about 7.5 to 10, is made up and the solution mixed with the emulsion at any convenient stage during its preparation, but preferably during ripening or just prior to coating.

The following examples are given for purposes of illustration only and are not to be considered in any way as being limitative of the present invention.

The novel stabilizers of the present invention can be prepared according to a series of reactions which can be structurally illustrated as follows:

HO OH (A) Preparation of m-chlorosulfonyl salicylic acid Ref. JCS 121, 2559.-Into a 250 ml. round-bottomed flask equipped with a stirrer, condenser and calcium chloride tube was placed 145.5 g. (1.25 m.) of chlorosulfonic acid. This was cooled in an ice bath whereupon 38 g. (0.25 m.) salicylic acid was slowly added over a period of approximately 60 minutes. After completing the addition, the flask contents were warmed to room temperature and then to 70 C., this temperature being maintained for approximately 60 minutes. The flask contents were then cooled and poured over ice. The white solid obtained upon filtration was washed several times with ice-H O and then dried in vacuo with CaCl Thirty-one (31) grams of product, identified as m-chlorosulfonyl salicylic acid was isolated. After recrystallization from benzene, the prodnot had a melting point of 165170 C.

(B) Preparation of 4,4'-dihydroxy diphenyl disulfide- 3,3'-dicarboxylic acid.A solution is prepared consisting of:

m-Chlorosulfonyl salicylic acid obtained from (A) g 31.5 Glacial acetic acid ml 520 57% HI ml 97.2

Example I Approximately 100 milligrams of 4,4'-dihydroxy diphenyl disulfide-3,3'-dicarboxylic acid, provided as a 0.5% methanolic solution was added to a silver halide emulsion containing 0.6 mole silver halide in the proportions of approximately 60 mole percent AgCl and 40 mole percent AgBr. The addition was effected just prior to coating at a time when the emulsion, in the liquid form, was made ready for coating. The so-prepared emulsion to which other ingredients such as hardeners, surfactants, stabilizers, bactericides and antimolding agents had been added was coated on paper and dried. A control coating prepared with the same emulsion but omitting the 4,4- dihydroxy diphenyl disulfide-3,3'-dicarboxylic acid was also coated on paper and dried. Upon examination of the respective prints following exposure and development it is observed that the sample containing the 4,4- dihydroxy diphenyl disulfide-3,3'-dicarboxylic acid exhibits a desirable black basic-image tone while the control exhibits a brownish-image tone. Moreover, the 4,4- dihydroxy diphenyl disulfide-3,3'-dicarboxylic acid containing print retained its black image tone on hot drying much more eflectively than the control.

6 Example II This example illustrates the use of the disulfide stabilizer of the present invention as an ingredient of a nonsensitized surface layer.

A 2% gelatin solution '(1 liter) was prepared to which was added 200 mg. of 4,4'-dihydroxy diphenyl disulfide- 3,3'-dicarboxylic acid. This solution was applied as a protective surface layer on top of a light-sensitive silver halide emulsion layer. A control coating was likewise prepared but omitting the stabilizer compound and similarly applied to an identical silver halide emulsion layer. On comparison of normally and hot dried prints, the results were similar to those obtained in Example I.

Example IH A silver halide emulsion in gelatin containing 2% silver iodide and 98% silver bromide was prepared in a. conventional manner and brought up to its maximum light sensitivity. It was then readied for coating; finals were added, such as sensitizing dyes and hardening agents. A 0.1% solution of 4,4-dihydroxy diphenyl disulfide-3,3'-dicarboxylic acid was added to the emulsion as an antifoggant and stabilizer. The emulsion which contained about 0.6 mole of silver halide was divided into 4 parts identified respectively as A, B, C, and D. Stabilizer (4,4-dihyd.roxy diphenyl disulfide-3,3-dicarboxylic acid) was added in the amounts indicated in Table I below. The s-o-prepared emulsion samples were coated on a suitable cellulose ester base and dried. Following exposure in a Type IB Sensit-ometer each of the samples was developed in indentical manner in a developer of the following composition:

Grams Metol 1.5

Sodium sulfite, anhydrous 45 Sodium bisulfite 1 Hydroquin-one 3 Sodium carbonate, monohydrated 6 Potassium bromide 0.8 Water to make 1 liter.

The following results were obtained:

TABLE Quantity of Oven (50 0.)

compound Relative Fog at 12 fog at 3' Sample used (mg) speed development development Example IV This example illustrates the use of the disulfide stabilizers of the present invention in an anti-abrasion layer.

A silver halide emulsion in gelatin containing 2 mole percent silver iodide and 98 mole percent silver bromide was coated on film base In well known manner. After coating, an aqueous gelatin solution containing 20 grams gelatin in 1 liter H 0 and 10 mg. 4,4'-dihydroxy diphenyl disulfide-3,3-dicarboxylic acid was coated thereon as an anti-abrasion layer. A control sample was prepared omitting the stabilizer and similarly coated. After drying, each of the samples was exposed and processed as described in Example III with the exception that the development was carried out at a temperature of F. The sample which did not contain the disulfide stabilizer developed to a fog of 0.25 after 8 seconds, whereas the test strip of the material containing the 4,4'-dihydroxy diphenyl disulfide-3,3'dicarboxylic acid showed a fog of only 0.12. Moreover, no loss in speed was detected.

Results similar to those described above are obtained when one or more of the stabilizer compounds of the present invention is added to one or more of the processing baths conventionally employed in the pre-development and post-development of an exposed silver halide photographic film. For example, significant stabilizing improvement is observed when such compounds are added to the developer bath, fixing solution, rinse bath and the like. Furthermore, results comparable to those described in the foregoing examples are obtained when the particular disulfide stabilizers described therein are substituted in equivalent amounts, within the range specified with one or more of the following compounds:

(i7 01H (I) 0211 Cl @ss y-ol OH OH bis 2-hydroxy-3chloro-S-carboxyphenyl disulfide 2) (3 2H CI 0 2H K s Q 0H 0 H bis (2-hydroxy-5-carb oxyphenyl) disulfide 3) CI 0 2H C 0 2H GENO-S s oom )H 6H -bis(2 hydroxy 3 methoxy carboxyphenyl)disulfide, etc.

The developer composition may be any of those conventionally employed in the development of exposed silver halide emulsions and accordingly, may be of the hydroquinone type, i.e., those which contain hydroquinone, potassium metabisulfite and potassium bromide, or they may be of the metol-hydroquinone type, i.e., those which contain p-methylaminophenol, sodium sulfite, sodium bisulfite, hydroquinone sodium carbonate, and potassium bromide. Alternatively, the developer composition may be of the so-called borax type, i.e., those which contain p-methylaminophenol, sodium sulfite, hydroquinone borax and potassium bromide.

The antifogging and anti-plumming characteristics of silver halide emulsions is likewise considerably improved in those instances wherein the stabilizer compound is included in a layer adjacent thereto. In the latter embodiment, the primary requirement is that the stabilizer compound be in intimate contact with the sensitized emulsion layer. Without intending to be bound by any theory, it appears that the stabilizer compound diffuses or otherwise migrates to the sensitized emulsion layer and especially when subjected to aqueous media.

It will also be understood that the novel stabilizers of the present invention may be employed singly or in admixtures comprising two or more of such compounds. Again, optimum combinations thereof can be readily ascertained in a particular instance by routine laboratory experimentation.

The present invention has been disclosed with respect to certain preferred embodiments thereof, and there will become obvious to persons skilled in the art various modiiications, equivalents, or variations thereof which are intended to be included within the spirit and scope thereof.

What is claimed is:

1. A light-sensitive silver halide emulsion containing an anti-fogging and anti-plumming material comprising a compound of the following general formula:

R000 CooR wherein R is a member selected from the group consisting of hydrogen, sodium; potassium; ammonium; NR R R R where R R R and R are members selected from the class consisting of hydrogen and alkyl of 1 to 4 carbon atoms and hydroxylalkyl in which the alkyl group contains from 1 to 4 carbon atoms and X is a member selected from the class consisting of hydrogen, chlorine, bromine, alkyl, alkoxy and hydroxylalkyl wherein the alkyl group in all instances contains from 1 to 4 carbon atoms, said compound being symmetrical with respect to the disulfide bridge and wherein the OH and -COOR groups occupy one of the positions ortho and para relative to each other, the COOR group being in a position meta to the disulfide bridge.

2. A light-sensitive silver halide emulsion according to claim 1 wherein said anti-fogging and anti-plumming material comprises 4,4'-dihydroxy diphenyl disulfide-3,3-dicarboxylic acid.

3. A light-sensitive photographic material comprising a base and at least one light-sensitive silver halide emulsion, said silver halide material containing an anti-fogging and anti-plumming material comprising a compound of the following general formula:

ROOG COOR ay- Q HO 1 OH X X wherein R is a member selected from the group consisting of hydrogen, sodium; potassium; ammonium; NR R R R where R R R and R are members selected from the class consisting of hydrogen and alkyl of 1 to 4 carbons atoms and hydroxylalkyl in which the alkyl group contains from 1 to 4 carbon atoms and X is a member selected from the class consisting of hydrogen, chlorine, bromine, alkyl, alkoxy and hydroxylalkyl wherein the alkyl group in all instances contains from 1 to 4 carbon atoms, said compound being symmetrical with respect to the disulfide bridge and wherein the OH and COOR groups occupy one of the positions ortho and para relative to each other, the COOR group being in a position meta to the di sulfide bridge.

4. A light-sensitive photographic material according to claim 3 wherein said anti-fogging and anti-plumming material is present in said light-sensitive silver halide emulsion layer.

5. A light-sensitive photographic material according to claim 1 wherein said anti-fogging and anti-plumming material is present in an auxiliary layer adjacent to said light-sensitive silver halide emulsion layer.

6. A light-sensitive photographic material according to claim 3 wherein said anti-fogging and anti-plumming material comprises 4,4'-dihydroxy diphenyl disulfide-3,3'-clicarboxylic acid.

7. An aqueous developer solution containing a silver halide photographic developing agent and an anti-fogging and anti-plumming material comprising a compound of the following general formula:

ROOO COOR wherein R is a member selected from the group consisting of hydrogen; sodium; potassium; ammonium; NR R R R where R R R and R are members selected from the class consisting of hydrogen and alkyl of 1 to 4 carbons atoms and hydroxylalkyl in which the alkyl group contains from 1 to 4 carbon atoms and X is a member selected from the class consisting of hydrogen, chlorine, bromine, alkyl, alkoxy and hydroxylalkyl wherein the alkyl group in all instances contains from 1 to 4 carbon atoms, said compound being symmetrical with respect to the disulfide bridge and wherein the OH and COOR groups occupy one of the positions ortho and para relative to each other, the COOR group being in a position meta to the disulfide bridge.

8. An aqueous developer composition according to claim 7 wherein said silver halide developing agent comprises hydroquinone.

9. A developer composition according to claim 7 wherein said anti-fogging and anti-plumming material comprises 4,4'-dihydroxy diphenyl disulfide-3,3'-dicarboxylic acid.

10. A process for the preparation of a photographic emulsion which comprises forming the emulsion, ripening the emulsion and during said ripening, adding thereto an anti-fogging and anti-plumming material comprising a compound of the following general formula:

ROOC COOR wherein R is a member selected from the group consisting of hydrogen, sodium; potassium; ammonium; NR R R R where R R R and R are members selected from the class consisting of hydrogen and alkyl of 1 to 4 carbon atoms and hydroxylalkyl in which the alkyl group contains from 1 to 4 carbon atoms and X is a member selected from the class consisting of hydrogen, chlorine, bromine, alkyl, alkoxy and hydroxylalkyl wherein the alkyl group in all instances contains from 1 to 4 carbon atoms, said compound being symmetrical with respect to the disulfide bridge and wherein the OH and COOR groups occupy one of the positions ortho and para relative to each other, the COOR group being in a position meta to the disulfide bridge.

11. A process for the preparation of a photographic emulsion which comprises forming the emulsion, ripening the emulsion, coating said emulsion on a base and adding to said emulsion just prior to the coating thereof on the support an anti-fogging and anti-plumming material comprising a compound of the following general formula:

ROOC 000R HO OH wherein R is a member selected from the group consisting of hydrogen, sodium; potassium; ammonium; NR R R R where R R R and R are members selected from the class consisting of hydrogen and alkyl of 1 to 4 carbon atoms and hydroxylalkyl in which the alkyl group contains from 1 to 4 carbon atoms and X is a member selected from the class consisting of hydrogen, chlorine, bromine, alkyl, alkoxy and hydroxylalkyl wherein the alkyl group in all instances contains from 1 to 4 carbon atoms, said compound being symmetrical with respect to the disulfide bridge and wherein the OH and --COOR groups occupy one of the positions ortho and para relative to each other, the COOR group being in a position meta to the disulfide bridge.

12. A process of treating an exposed silver halide emulsion characterized in that at least one of the processing baths employed in the development and treatment of said emulsion contains an anti-fogging and anti-plumming material comprising a compound of the following general formula:

ROOC GOOR wherein R is a member selected from the group consisting of hydrogen, sodium; potassium; ammonium; NR R R R Where R R R and R are members selected from the class consisting of hydrogen and alkyl of 1 to 4 carbon atoms and hydroxylalkyl in which the alkyl group contains from 1 to 4 carbon atoms and X is a member selected from the class consisting of hydrogen, chlorine, bromine, alkyl, alkoxy and hydroxylalkyl wherein the alkyl group in all instances contains from 1 to 4 carbon atoms, said compound being symmetrical with respect to the disulfide References Cited UNITED STATES PATENTS 3,226,232 12/1965 Dersch et al 96l09 OTHER REFERENCES The Naming and Indexing of Chemical Compounds by Chemical Abstracts, 1957, p. 5945.

J. TRAVIS BROWN, Primary Examiner. C. E. DAVIS, Assistant Examiner.

US. Cl. X.R. 9650, 61, 109 

